DA 70 Series - Manual
Contents
1. for more details Speaker Outputs Each Channel has a phoenix type connector which may be used to con nect loudspeakers See Output Wiring in the section on Installation Page 13 for more de tails AC Power Connection All DA 70 Series amplifiers are equipped with a IEC socket on the rear apron for AC connections Models DA 70 2 and DA 70 4 may only be connected to 120VAC mains Models DA 70 2 PFC and DA 70 4 PFC are Power Factor Corrected and may be connected to any AC main voltage from 90VAC 240VAC 10 Installation Mechanical considerations The Stewart Audio DA 70 Series amplifier occupies just one half standard rack space is only 10 6 deep and weighs just over 3 pounds making it easier to install and transport than almost any other comparable power amplifier Still some precautions are in order Rack mounting of the DA 70 Series may be achieved by using either the Stewart Audio RMK 70 S or RMK 70 D rack kits The RMK 70 S centers the amplifier in a single rack space while the RMK 70 D allows you to rack two amps side by side in a single rack space For stability always use four screws to affix the amplifier to the rack preferably using rack washers to avoid cosmetic damage to the rack mount panels When rack mounting your DA 70 Series amplifiers be sure to remove the four adhesive rubber feet from the bottom of the unit The DA 70 Series amplifiers can also be mounted to a standard rack shelf or used as a stand a2. Connectors one for each channel NOTE Do not attempt to Bridge this amplifier or tie the commons together Serious damage to your amplifier may occur if this is attempted Total Protection The DA 70 Series amplifiers employ circuitry which fully protect the ampli fier while avoiding sonic compromise Front Panel Simplicity is a design objective in the development of all Stewart Audio power amplifiers These amplifiers remain simple and intuitive to operate even while incorporating some of the most advanced technology available today Power On Off and LED Clip Indicators The front panel provides visual feedback of the amplifiers status The front panel power switch is accompanied by an LED which will illuminate upon power up Note there is an initial delay of up to 30 seconds when the am plifier is first turned on Additional LEDs one for each channel will illumi nate when the amplifier is being pushed into clipping Level Controls The DA 70 Series has been equipped with a level control for each channel conveniently located on the front panel With typical program level present adjust each channel to provide the desired output level If undesirable dis tortion is present check preceding components and make necessary ad justments 9 Rear Panel Inputs Each Channel has a phoenix type connector which may be used with ei ther balanced or unbalanced lines See Input Wiring in the section on Installation Page 13
3. the enclosure being used and how hard the amplifier is working In extreme cases it might be necessary to install a cooling fan in the rack for additional cooling In free standing installations where the amplifier is sitting on a shelf or hard floor the four rubber feet must remain mounted to the bottom of the amplifier Under no circumstances should the amplifier be placed directly on carpeting or similar surfaces AC Power Considerations Your Stewart Audio DA 70 2 and DA 70 4 amplifiers are designed to operate on 120 volt 60 Hz AC current Your Stewart Audio DA 70 2 PFC and DA 70 4 PFC amplifiers are designed to operate over a range of 90 volts 240 volts 50 60 Hz alternating current Average power consumption will depend on load impedance signal level and program material Typical power consumption in Amperes All channels driven 4 Ohms 120V AC Model Idle 1 8 power _ 1 3 Power _ Full Power DA 70 2 0 2 0 4 0 6 1 4 DA 70 4 0 3 0 7 1 3 3 0 DA 70 2 PFC 0 2 0 4 0 7 1 6 DA 70 4 PFC 0 3 0 8 1 4 3 2 12 Input Wiring Your DA 70 Series amplifier is provided with a 3 conductor Phoenix Type connector for each input The connector may be wired Balanced by connecting to Signal ground Signal and Signal as marked on the chassis over each input If you wish to operate the amplifier unbalanced connect your unbalanced line across Signal ground and Signal and add a jumper from Signal to Signal ground Output Speak
4. STEWARTAUDIO The Difference is Hear DA 70 Series Professional Power Amplifiers Owners Manual Safety Before using your Stewart Audio Power Amplifier please read this owner s manual carefully to ensure optimum trouble free performance Warning To REDUCE THE RISK OF ELECTRI CAL SHOCK DO NOT EXPOSE THIS AMPLIFIER TO RAIN OR MOISTURE DANGEROUS HIGH VOLTAGES ARE PRESENT INSIDE THE CHASSIS DO NOT OPEN THE COVER REFER SERVICING TO QUALIFIED PERSONNEL ONLY CAUTION RISK OF ELECTRICAL SHOCK DO NOT OPEN CAUTION TO REDUCE THE RISK OF ELECTRICAL SHOCK DO NOT REMOVE COVER OR BACK NO USER SERVICABLE PARTS INSIDE REFER SERVICING TO QUALIFIED SERVICE PERSONENEL The lightning flash with arrowhead symbol within an equilateral A N triangle is intended to alert the user to the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electrical shock to persons The exclamation point within an equilateral triangle is intended to alert the user to the presence of important maintenance servicing instructions in the literature accompanying the appliance Important Safety Instructions Please Read Prior to Product Installation All of the safety and operating instructions should be read be fore the amplifier is operated Retain these instructions for fu ture reference All instructions should be followed all warnings on the ampl
5. charging reduces power supply sagging common with other designs The New DA 70 Series Digital Amplifiers utilizes a new regulated forward converter design Switch Mode Power Supply operating at a fre quency 2 3 faster than our old standard supply Power Factor Correction Models with a PFC designation utilizes Power Factor Correction circuitry in their power supply This circuitry automatically adjusts the power supply to provide stable full output over a wide range of mains voltages typi cally from 90VAC to 240VAC This feature makes the DA 70 Series oper able anywhere in the world and is a very useful feature when operating from unstable or questionable AC mains This power supply s remarkable conversion efficiency combined with Damped Ternary Modulation translates into major savings of energy drawn from the AC line The benefits are reduced heat dissipation and downsizing of most major components This saves space and weight without sacrificing the Sonic excellence Stewart Audio is famous for Bridging Bridging of the DA 70 Series is not possible due to the high efficiency design of the Damped Ternary Modulation Balanced Unbalanced Inputs All DA 70 Series amplifiers feature Phoenix Type input Connectors which will accept either balanced or unbalanced signals See Input Wiring in the section on Installation Page 13 for more details Output Connections All DA 70 Series amplifiers feature Phoenix Type output
6. er Wiring Your DA 70 Series amplifier is provided with a two conductor Phoenix Type connector for each output The connector may be wired by connecting the speaker line to and as marked on the chassis over each output Caution Due to the ternary design of the output stage Bridging of this product line is not possible Do not tie any output pin to any other pin or to ground Never con nect any speaker terminal to anything other than a single output pin WARNI NG Violation of this Caution may result in damage to your amplifier and will void your Stewart Audio Warranty 13 Trouble shooting If you experience difficulty in operating your new DA 70 Se ries amplifier Chances are good that you will be able to rem edy the problem yourself using standard troubleshooting techniques and the suggestions offered in the troubleshoot ing table on the next page When wiring cables it is imperative that all connections be made cleanly with no stray wire strands to short terminals Make sure the wire clamp screws are tight For proper con nection all wire should be stripped to bare approximately 1 4 inch of wire Make sure that the connector set screw seats on copper not insulation Keep in mind that other components in the system can cause problems which may appear to be caused by the amplifier systematic troubleshooting will allow you to isolate the source of difficulty If you fail to correct the problem by following the out
7. er components 6 What is the efficiency advantage of the DA 70 Series over other amplifier designs As shown in the figure below the ternary design has a 20 advantage over binary Class D at music levels typically 15 offull scale and about 3 times the efficiency of analog amplifiers B 12 Ydc 1kHz Rload 4 ohm 100 ED EFFICIENCY in 0 1 z 4 5 5 FP 3 a 10 11 12 OUTPUT POWER in Watts The Power Supply The foundation of all amplifier design is the power supply For years Stewart Audio has pioneered leading edge power supply technology All Stewart Audio amplifiers feature a High Frequency Switch Mode Power Supply Because of this use of advanced technology some explanation is in order Conventional Power Supplies operating at 60Hz standard line frequency recharge only 120 times per second requiring their storage capacitors and transformers to be quite large to supply the energy needed during the intervals between cycles when power is not available from the wall The power supply must act as a local reservoir of power from which the amplifier circuits draw This storage function is responsible for much of the bulk weight and cost of traditional power amplifiers High Frequency Switch Mode Power Supplies Stewart s famous High Frequency Switch Mode Power Supplies fully re charges 1000 times faster than conventional supplies requiring far less capacitance for filtering and storage This high speed re
8. et gain by turning amplifier volume all the way down set preamp level to normal turn up amplifier volume to desired level Check signal source for noise Long unbalanced lines can cause noise change to balanced lines See set gain above 15 Specifications 8 Ohm Stereo Power 4 Ohm Stereo Power Frequency Response 0 0 5 dB 1W Full Power Bandwidth 20 Hz 20 kHz Signal to Noise THD N Input Sensitivity Standard Voltage Gain Input impedance Balanced Unbal anced Class Input Connectors Output Connectors Power Supply Cooling Controls LED Indicators Construction Dimensions height width depth Max Weight Warranty 35 Watts Ch 70 Watts Ch 20 Hz 20 kHz 7 dB gt 93 dB lt 25 1V 0 dBV 17X 25 dB 20k Ohms 5k Ohms Damped Ternary Modulation Phoenix Type Phoenix Type High Speed Switching Convection No Fans Power on off Channel Gain Power amp Clip Steel amp Aluminum Chassis 1 75 H x 8 26 W x 10 6 D 3 4 Ibs 1 54 kg 3 years Parts amp Labor 16 Notes Stewart Audio 1000 Technology Drive Columbia Ca 95310 Tel 209 588 8111 Fax 209 588 8113 www Stewartaudio com
9. for future reference Special Features Stewart Audio s new Compact Series Power Amplifiers utilizes the latest in Digital Au dio Technology The new all Digital DA Series Power Amplifiers were developed by Stew art Audio s Digital Audio Team and represent the pinnacle of Stewart Audio technology and design Please take a few moments to read through this section of the manual which provides an overview of the features that makes this amplifier unique How is the DA 70 Amplifier different from other Amplifiers The primary difference between the DA 70 Series and other amplifiers is that it is all digital and it has much higher effi ciency Current digital audio systems use Class A B amplifiers to amplify analog signals produced by a DAC Analog designs have low efficiencies because of the power consumed in the active components as a result of the voltage difference be tween the amplifier s output and it s power supply This con tinuous control of the supply voltage results in peak efficien cies of about 50 As a result a large power supply and heat sink are required Class D switching amplifiers were developed to overcome this problem by discretely connecting the load to the power supply Higher efficiency is achieved but Class D is still essentially an analog solution because it utilizes an analog interface and con trol Stewart s approach was to develop a new Class D ampli fier that utilized digital control This approac
10. gn and quality workmanship has provided its customers with a unique combination of performance and reliability This commitment to excellence has gained the respect of industry professionals around the world The DA 70 Series Professional Series Power Amplifier utilizes a new high speed switching power supply and Damped Ternary Modulation Digital output topology The amplifier will deliver over 70 Watts of power per channel and may be purchased in either a 2 or 4 channel configuration This remarkable performance comes in a very compact package weighing a mere 3 4 pounds and occupying just one half standard rack space The DA 70 Series Amplifiers are convection cooled and require no noisy fans for cooling We at Stewart Audio strive to bring you the finest in professional electronics and we thank you for your choice which we see as an appreciation for our efforts The Stewart A udio Design Team Contents SpECial FeaLUeS ana A AO Odo kt Front Panel FeatureS u u umamamamacemawmamamimiewi Rear panel Features u mamamama mama mimananawamaswia NStANAUO sandra PECO aid aoi z we eat MFOUDIESIIOOUING nz nA OO da KEEP ches Technical Information am asa mama mae maa emama zz mimi For The Record 10 11 12 13 17 In the spaces below record the Model Serial number and Purchase information of your Power Amplifier Model Number Serial Number Purchase Date Retain this information
11. h enables lower cost through digital integration as well as eliminating per formance degradation due to analog component variations What is Damped Ternary Modulation Conventional Class D amplifiers utilize binary or Bl state operation Bi nary consists of only two switching states positive power and negative power Ternary or tri state operation consists of three switching states positive negative and a zero power state The third state is unique to this design During the time when neither supply connection is required both speaker terminals are connected to each other providing damping to the loudspeaker hence the name damped ternary The figure below shows the advantage of the damped ternary compared to binary modulation for a sine wave In binary the cancellation of two full level signals is required for small outputs Thus the amplifier is continuously providing full output This represents wasted power It also produces unwanted RF energy that must be kept from radiating In contrast the damped ternary design only supplies power to produce a signal Binary Signal Damped Ternary Signal Unused ignal Damping Net Signal T ___ Damped Ternary Advantage over Binary In tests using the same hardware configured for ternary and then for bi nary ternary s high frequency energy at zero output is attenuated over 20 dB below binary operating into the same filter This means higher effi ciency and smaller filt
12. ifier and in the operating instructions should be ad hered to This amplifier should not be used near water for example near a bath tub washbowl kitchen sink laundry tub in a wet basement near a swimming pool etc The amplifier should be situated so that its location and posi tion do not interfere with its proper ventilation For example the amplifier should not be placed on a rug sofa or similar surface which impedes the airflow across the chassis Airflow through the ventilation openings should be unobstructed The amplifier should only be connected to a properly grounded AC outlet as indicated under AC Power Connections in this manual Do not defeat the ground or polarization of the power plug Route all power cords and other cables so that they are not likely to be walked on tripped over or stressed Pay particular attention to condition of cords and cables at plugs and the point where they exit from the amplifier To prevent risk of fire or injury damaged cords and cables should be replaced imme diately Clean the amplifier with a damp cloth Do not use solvents or abrasive cleaners Never pour any liquid on or in the amplifier The amplifier should only be serviced by qualified service per sonnel Introduction Congratulations You have just purchased a new state of the art Digital Power Amplifier which will provide you with many years of reliable service Stewart Audio s commitment to innovation in desi
13. lined chart on the next page do not attempt to open or repair the unit yourself Please contact Stewart Audio at 209 588 8111 to ob tain a Return Authorization RA Number and shipping instructions Once an RA Number is obtained return the unit to Stewart Audio at the address indicated on the RA Form Refer to the enclosed Warranty information for Terms and Conditions of Warranty 14 Troubleshooting Reference Chart Symptom No output Power indicator is off There is a normal delay of up to 30 seconds on turn on No output Power indicator LED cy cles on and off Power indicator on no output from one or more channels Low volume in one or more chan nels Amplifier overheats and or shuts off Distorted output Noise on output Recommended Action Be sure power outlet is live Be sure power switch is on This indicates a short circuit condi tion on the output Disconnect speaker wires and turn amplifier power switch on If amp stays on the problem is in the output wiring or speakers Check input level controls input and output cables input signal and speakers Check input level controls input wir ing and input signal levels Be sure speakers are the same impedance Review section on Thermal Considerations Check clip lights for indication of overdriving NOTE overdriving for a long period of time can cause thermal shutdown Check input signal level and signal source S
14. lone product Ther mal Considerations Cooling of the DA 70 Series amplifiers is achieved by Stewart s unique whole chassis heatsink design which utilizes the entire chassis as a heatsink to cool the heat generating components inside In the event the internal ambient temperature reaches 85 degrees centigrade the protection circuit will shut down the power supply until the amplifier cools down Although the sophisticated thermal management system in the DA 70 Series makes it less susceptible to overheating than other amplifiers it remains good practice to provide airspace around the chassis NOTE A 4 model 4 channel amplifier will dissipate twice the heat of a 2 model 2 channel amplifier and a PFC model will dissipate approximately 10 more heat than a non PFC model Therefore while a DA 70 2 runs very cool the DA 70 4 PFC will require a little more attention to cooling Multiple amplifiers can be racked on top of one another without leaving a full rack space between them as long as sufficient airflow is maintained to allow heat to escape out the top 11 If mounted in a sealed rack leave the top and bottom spaces open to create a chimney effect within the rack which will provide cooling as air is drawn in the bottom and exhausted out the top The amount of airflow necessary will be determined by a number of factors including ambient temperature the amount of heat generated by other equipment in the rack the properties of
Download Pdf Manuals
Related Search